$12.99 Hi-Viz waterproof bag from the marine section of Academy Sports & Outdoors + flat bungie cord & reflective stickies I already had = $60 – $100 saved.
I also added a $10.99 Pelican mini flasher: water-resistant, durable red LED w/over half a mile visibility & 130 hours of burn-life (batteries included).
No joggling or “unseating” of loaded bag on maiden voyage of 37 miles, over lots of chip seal & speed bumps, through more gouged asphalt & cracked concrete than you could shake a stick at, up & down 2 bridges, top speed of 27 mph.
Yep, cheap & crafty, that’s how I roll!
Let me know if you have any mounting questions ~ ~ ~